The Nivallan sea urchin was an aquatic animal.
After Spock and T'Pring inadvertently swapped bodies during a Vulcan soul-sharing in 2259, Doctor Joseph M'Benga applied a paste made from ground Nivallan sea urchin to their foreheads as part of a successful procedure to switch them back. He noted that the paste was nutrient-rich, water-resistant, and a good electromagnetic match for Vulcan skin. M'Benga was also confident that its usage would eventually become Federation standard. (SNW: "Spock Amok")